A wide variety of materials has been used in affinity chromatography as carrier. The most widely used is beaded agarose which is activated with cyanobromide (CNBr). Although quite stable in aqueous solutions, its thermal and mechanical stability is not adequate for a variety of purposes, such as HPAC. The cyanobromide activation has the disadvantage that coupling of amines results in the formation of N-substituted isourea bonds which lack adequate stability. Such instability results in the leakage of ligands and after some time columns of such material acquire ion exchange properties which interfere with the biospecificity.
Silica, which has adequate mechanical stability and permanent porosity, has been considered to be unsuitable as support due to the irreversible adsorption and denaturation of certain substrates by the silanol groups on its surface. This has prevented the use of silica as carrier in affinity chromatography and in similar uses. Regnier and Noel, J of Chromatographic Science 14 (1976) 216, have provided a modified silica providing glycerolpropylsilane bonded phases. These are of a thickness of about 18-19 .ANG., with the glycerol moiety varying from 80 to 150 .mu.moles/g.
The substrate used was controlled porosity glass, and the modification decreased nonspecific adsorption and denaturation of proteins. The modified silica of Regnier et al., has two adjacent carbons, each bearing a hydroxy group, and activation is likely to lead to the formation of undesired inactive cyclic carbonate derivatives. This drawback is overcome to a large extent by the present invention.